228128721 has 16 divisors (see below), whose sum is σ = 314918400. Its totient is φ = 146741760.

The previous prime is 228128713. The next prime is 228128759. The reversal of 228128721 is 127821822.

It is not a de Polignac number, because 228128721 - 2³ = 228128713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (228128711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29355 + ... + 36303.

It is an arithmetic number, because the mean of its divisors is an integer number (19682400).

Almost surely, 2^228128721 is an apocalyptic number.

It is an amenable number.

228128721 is a deficient number, since it is larger than the sum of its proper divisors (86789679).

228128721 is a wasteful number, since it uses less digits than its factorization.

228128721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7336.

The product of its digits is 7168, while the sum is 33.

The square root of 228128721 is about 15103.9306473514. The cubic root of 228128721 is about 611.0264193733.

The spelling of 228128721 in words is "two hundred twenty-eight million, one hundred twenty-eight thousand, seven hundred twenty-one".